Kaempferia galanga L. Extract and Its Active Component Suppresses Cell Proliferation by Inhibiting S Phase Progression in Ehrlich Ascites Tumor Cells

Objectives: Kaempferia galanga L. is a plant of the ginger family that is mainly cultivated in Asia, and has various physiological effects. However, the anticancer effects of Kaempferia galanga L. have not been well revealed. In this study, we investigated the anticancer effects and detailed mechanism of Kaempferia galanga L. Methods: Ehrlich ascites tumor cells (EATC) were cultured with or without Kaempferia galanga L. extracts (KGE) or ethyl p-methoxycinnamate (EMC), a main component of KGE. The viability and proliferation of EATC was measured using a trypan blue assay. Cell cycle analysis was conducted with bromodeoxyuridine assay and flow cytometry. Furthermore, we performed quantitative reverse transcription PCR, western blotting and rhodamin-123 stain to investigate the detailed mechanism of anticancer effect of EMC. For in vivo studies, female ICR mice were injected intraperitoneally with EATC, and orally administered with KGE and EMC for 13 days. Results: KGE suppressed the proliferation of EATC without significantly change cell viability, and inhibited S phase progression. EMC also inhibited the proliferation of EATC by inhibiting S phase progression. Furthermore, cyclin D1 expression level was downregulated and p21 expression level was upregulated by EMC treatment. EMC also suppressed mitochondrial transcription factor A (TFAM) expression, but had no significant effect on mitochondrial membrane potential and mtDNA copy number. TFAM may regulate cyclin D1 and p21 expression rather than mitochondrial function. Moreover, EMC decreased the phosphorylation level of c-Myc, which is a transcription factor of TFAM. In addition, in vivo experiments showed that ascites volume was significantly increased in EATC-bearing mice, but this increase was suppressed by oral administration of EMC or KGE. Conclusions: These results indicate that EMC is the active component of the anticancer effect of KGE and suppresses the proliferation of EATC by inhibiting S phase progression through regulating the expression of cyclin D1 and p21. Furthermore, this study provides new insights into the role of TFAM in the anticancer effects of natural compounds. Funding Sources: This work was supported by JSPS KAKENHI.